Twitter was used to break the news to diners that branches in Chiswick and Holborn, in London, plus another in Winchester, Hampshire, are closing. The Covent Garden branch, in central London, is staying open.

The tweet said: "It's no secret that the industry has been affected by the tough climate& a proposal has been made to close UJ Chiswick, Holborn&Winchester.

"We'd like to say a huge thank you to everyone,we have loved meeting you all. Please do pop along to our Covent Garden Piazza restaurant."

Fish and chips costs £15 and pizza from £11 at the chain, which is billed as being "all about bringing back nostalgic British classics using the best artisanal ingredients".

It was launched in 2011 with US pizza restaurateur Chris Bianco.

A spokesman for the TV chef said: "The Jamie Oliver Restaurant Group has made the decision to close three of the Union Jacks restaurants.

"After a full review it was concluded that the businesses in Winchester, Chiswick and Holborn were no longer sustainable in the current challenging climate. The Union Jacks site in the Piazza in Covent Garden is trading well and will remain fully operational.

"The group is confident in being able to deliver a robust performance in 2014 and is looking forward to a number of restaurant openings, in the UK and internationally. This will include developing the successful Trattoria model which is doing well in its first location in Richmond."